The invention relates to an open-mouthed bag having a multiple paper ply construction with a sealable plastic liner.
More specifically, the invention is directed to a type of bag having a satchel bottom with the paper plies adhesively attached but freely foldably retaining the bottom of a plastic liner or pouch at the satchel bottom end of the bag. The opposite end of the bag is open and conventionally constructed to allow for the heat sealing of the plastic liner when filled, and the subsequent severing thereof, thereby rendering the plastic liner detachably removable from the bag. The paper plies at the open end of the bag may be provided in a stepped construction for adhesive bonding after being folded in a pinched closure but might otherwise be flush cut for a sewn closure, including an optional tear strip, or have other forms of known closures.
The invention is also related to providing a bag that is tubular and as a blank may be stacked in a flat condition for later use by the packager, wherein the plastic pouch and multiple ply papers at the bottom of the bag are cooperative so that the bag may be filled with a product, such as dry granulated powder, without tearing the plastic liner. The satchel end of a filled bag would preferably have a flat rectangular bottom.
The invention is more specifically aimed at providing a satchel bottom polyethylene ("poly") lined bag that eliminates the sharp comers inherent in conventional pinch bottom open mouthed (PBOM) type of closures for tubular bags, so that when the bags are filled and stacked on a pallet, they achieve relatively smooth pallet edges and will not puncture the usual load-securing plastic stretch wrapping that envelops a loaded pallet. This also renders the bag less susceptible to impact damage otherwise experienced at the pointed corners of PBOM bags if contacted by other objects, such as when roughly handled by a forklift truck during stacking and unstacking.
The invention also provides for a plastic liner construction as in U.S. Pat. No. 5,281,027, so that the bag may be formed on conventional stepped tubing equipment. The present bag, however, provides for forming a sealed bottom end of a plastic liner that is folded at a multiple ply paper satchel bottom in a freely folded relation therewith. Accordingly, the present invention is an improvement in the art and upon this patented bag, which utilize a pinch bottom non-satchel closure.
The invention additionally overcomes the prior art deficiencies as found in the satchel bottom bag disclosed in U.S. Pat. No. 3,929,275. This patent provides a straight-cut, non-stepped bottom for the paper plies wherein all the paper layers are slit. It also does not show marginal offsetting at a plastic liner in a stepped multi-paper ply satchel bottom bag to prevent pinholing or rupture during filling. Contrarily, in the present invention, the innermost paper ply adjacent the plastic liner is not slit. The innermost paper ply thereby offers an underlying reinforcing and rigidifying continuous lower edge when folded into the satchel closure.
Another known satchel bottom bag utilizing a plastic liner is provided by Stone Container Corporation in a bag identified as PEELPACK. This bag does not slit any of the multiple paper plies and therefore does not achieve the effective geometric multi-zone gluing pattern for the paper plies as in the present invention.
The prior art also has taught the use of gussetted bags that form a square bottom and achieve a fairly acceptable configuration on a pallet to avoid damage. However, the industry has the need for filling satchel bottom bags on the same filling equipment as used for flat tubular PBOM bags. Gussetted bags must be filled on different types of fillers. This is because gussetted bags do not have a flat tubular construction and therefore are incapable of being filled on the flat tube bag filling equipment.
The invention also has the goal of providing a plastic liner for a tubular flat bag that is heat sealable and able to be folded flat in a loose arrangement for a satchel bottom bag rather than a PBOM bag.
The present invention satisfies the above needs and overcomes the deficiencies in the prior art as will be described in greater detail hereinafter.